A new, simple technique for estimating the parameters of the two-term Philip infiltration equation was developed and tested using field-measured data obtained in the northern Chihuahuan desert of New Mexico. The technique simultaneously provided information on the relationship between the Philip equation parameter A, and the field-measured hydraulic conductivity. The equation was reformulated as I - cKf = 1/2St-1/2, where I is the infiltration rate, S the sorptivity, t the time, Kf the field-measured final infiltration rate, and c, a coefficient relating Kf to the Philip parameter A. The final, steady infiltration rate measured in the field was used for the value of Kf. Regressions of (I - cKf) vs. (1/2t-1/2) for values of c between 0 to 1 resulted in optimum values for each treatment along with their corresponding S values. For the soils in this area, values for the coefficient c were somethimes outside the suggested range of 0.33 to 0.67, and were different for each study site. The regression analysis also showed that the value of S can be highly sensitive to changes in c. Using the values of S and c determined by the proposed method, a comparison was made between computed infiltration rates and measured infiltration rates. The results of this study showed that the prediction method provided adequate fits to field-measured data, and that the choice of an appropriate c factor is important in determining infiltration parameters from field data.

%B Soil Science Society of America Journal %V 50 %P 1319-1323 %8 1986 %G eng %U files/bibliography/JRN00035.pdf %M JRN00035 %L 00445 %F 38